This invention relates to a plant control method.
In order to operate, for example, a thermal power plant stably and at high efficiency, it is important that the temperature of main steam generated by a boiler is kept constant without being affected even by the disturbances of a load change etc. In starting the plant, the main steam temperature needs to be raised correctly in accordance with a predetermined heating curve.
To the end of enhancing the controllability, various systems have heretofore been developed. The inventors of the present application have also proposed the system of U.S. Pat. No. 3,877,636. The patented invention derives the desired value and predictive value of the main steam temperature after a predetermined time by means of a computer which mathematically models the the characteristics of a boiler, and controls the starting of the boiler so as to render the difference of both the desired and predictive values null. Although this system has achieved a certain result in the enhancement of the controllability, a more enhanced performance is desired. Further, the proposed system needs to be made applicable also to the steady load operation.
One of the reasons why a fully satisfactory performance is not obtained even with the aforecited invention is that the characteristics of the boiler cannot be correctly simulated. Another reason is that the characteristics vary depending upon the operating conditions.